Mobile-pole lifter for moving ferromagnetic loads

ABSTRACT

A magnetic lifter includes at least one dipolar mobile pole ( 1 ) consisting of two ferromagnetic pole pieces ( 2, 3 ), joined through an elastic connection, and inserted between two fixed opposite polarities ( 5, 6 ) of an electromagnet ( 7 ) so as to be able to slide within a housing ( 8 ) formed therebetween. By using as mobile poles ( 1 ) dipoles which slide between two poles ( 5, 6 ) of opposite polarity the closure of the magnetic circuit occurs within the single mobile pole ( 1 ) whereby the contact losses are reduced to half and it is possible to lift even small- and medium-sized loads with the greatest ease. Moreover, thanks to the elastic connection between the two pole pieces ( 2, 3 ) which allows a change in their mutual distance, upon activation of the lifter the two pole pieces ( 2, 3 ) tend to move away from each other until they adhere through magnetic attraction each one to its own adjacent polarity, thus canceling the air gaps and the consequent leaks as well as the risks of sliding.

The present invention relates to magnetic lifters used to moveferromagnetic loads, and in particular to a mobile-pole lifter of newdesign.

It is known that existing mobile-pole lifters (electromagnets,electropermanent or permanent magnets) are mainly used to lift loads offerromagnetic steel with an uneven contact surface such as rows ofbillets, round bars, tubes, etc. These mobile poles are intended topartially make up for the differences in height between the singleelements of the load thus increasing the performance of the lifters, butto date they have always been inserted each one as a monopole in theseat of a pole to act as a sliding pole piece. In other words, even inlifters provided with one or more rows of mobile poles each of them isjust an extension of a South pole or of a North pole.

However, these known lifters have a series of drawbacks stemming fromthis structure which can be summarized in the following points:

-   a) in order to allow the sliding of the mobile poles there are    provided structural air gaps between the latter and the fixed poles,    however these air gaps get wider in time due to the wear caused by    the sliding friction between the two parts (e.g. from the initial    0.5 mm to 2 mm and more), and this leads to a significant magnetic    leak with consequent decrease of the lifting capacity;-   b) also due to the air gaps, known lifters produce the maximum lift    only when the mobile poles are completely extracted, i.e. in the    only position where the mechanical restraint preventing their    further extraction prevents them from sliding under load;-   c) since the mobile poles are monopoles, they have to lead the flux    lines of the magnetic field from the pole in which they are    inserted, passing through the load, to an adjacent pole of opposite    polarity (as all poles are only North or only South), which results    in doubling the contact losses;-   d) for the same reason, with known lifters it is almost impossible    to lift loads of small or medium size since it is not possible to    short-circuit the two polarities North and South on a single element    in a suitable and effective way.

Therefore the object of the present invention is to provide a magneticlifter which is free from said drawbacks. This object is achieved bymeans of a magnetic lifter wherein the mobile poles are dipoles slidingbetween two poles of opposite polarities, each mobile pole consisting oftwo elastically connected pole pieces. Other advantageous features ofthe present lifter are disclosed in the subsequent claims.

A first main advantage of the present lifter stems from the fact that byusing as mobile poles dipoles which slide between two poles of oppositepolarity the closure of the magnetic circuit occurs within the singlemobile pole. This results in the contact losses being reduced to halfand in the possibility of lifting even small- and medium-sized loadswith the greatest ease.

A second significant advantage results from the elastic connectionbetween the two pole pieces acting as poles of the mobile dipole, sincethanks to such elasticity their mutual distance can change. In otherwords, upon activation of the lifter the two pole pieces tend to moveaway from each other until they adhere through magnetic attraction eachone to its own adjacent polarity, thus canceling the air gaps and theconsequent leaks as well as the risks of sliding.

Further advantages and characteristics of the lifter according to thepresent invention will be clear to those skilled in the art from thefollowing detailed description of some embodiments thereof, withreference to the annexed drawings wherein:

FIG. 1 is a diagrammatic front view in vertical section of a firstembodiment of a lifter according to the invention;

FIG. 2 is a view similar to the preceding one which shows an enlargeddetail of the mobile pole at rest, i.e. when the lifter is not active;

FIG. 3 is a view similar to the preceding one which shows the mobilepole in a load engagement state, i.e. when the lifter is active;

FIGS. 4 and 5 are diagrammatic side views in vertical section takenalong line A-A of FIG. 1 which show two variations of said firstembodiment; and

FIGS. 6 and 7 are diagrammatic front views in vertical section whichshow other two variations in number and arrangement of the poles.

Referring first to FIGS. 1-3, there is seen that the novel aspect of thelifter according to the present invention is that of including a dipolarmobile pole 1 made up of two ferromagnetic pole pieces 2, 3 joinedthrough an elastic connection consisting of an elastomer 4. Said mobilepole 1 is inserted between two opposite polarities 5, 6 of anelectromagnet 7 so as to be able to slide within a suitable housing 8formed therebetween, with the two pole pieces 2, 3 respectively adjacentto a North polarity and a South polarity.

The shape of pole pieces 2, 3 and of polarities 5, 6 is conventional andallows to prevent the slipping out of the mobile pole 1, and it providesan air gap T which in time may significantly increase in width due towear.

The operation of the present lifter is very simple and effective and isreadily understood: the mobile pole 1 gets in contact with theferromagnetic load 9 to be lifted and, upon activation of theelectromagnet 7, the two pole pieces 2, 3 tend to move away from eachother until they adhere through magnetic attraction each one to its ownadjacent polarity 5, 6 by dilating elastomer 4 as required, so that theytoo become a North polarity and a South polarity and substantiallycancel the structural air gaps T and the consequent leaks.

At this moment each dipole is put in the condition of being able toeffectively lift a single load with a minimum contact loss and nosliding problems, even if pole 1 is partially retracted, since there isa direct magnetic lock on the North and South polarities of the lifter.

Elastomer 4 is designed to have an elasticity suitable for the lifterpower, so as to allow a complete cancellation of the air gaps T duringoperation while maintaining the capacity of moving near again the polepieces 2, 3 even after many operating cycles to guarantee a smoothsliding of the mobile pole 1. For example vulcanized rubber with a Shorehardness in the range of 50-60 may be used, to which the pole pieces 2,3 are secured by gluing or through fastening means (e.g. bolts).

A further advantage of said mobile poles 1 coming from the presence ofelastomer 4 is their capacity of absorbing possible bumps even to asignificant extent without damages.

The longitudinal sectional views of FIGS. 4 and 5 illustrate how thelifter may include a single long mobile pole or a row of independentmobile poles which are however enclosed between only two fixed poles 5,6. Obviously there is also provided the arrangement, similar to theconventional one, of a series of mobile poles sliding between as manypairs of fixed poles.

The frontal sectional views of FIGS. 6 and 7 illustrate how the liftermay include two (rows of) mobile poles 1 side to side which share afixed “two-faced” central pole 6′, or a single pole (or row of poles) 1combined with a further fixed pole 5″ which operates in cooperation witha central fixed pole 6″ of greater width.

It is clear that the above-described and illustrated embodiments of thelifter according to the invention are just examples susceptible ofvarious modifications. In particular, the elastic connection between thepole pieces 2 and 3 could be achieved by any other material which inaddition to make physically integral the dipole allows for the necessaryoperating elasticity; such as clothes of various fabrics, sheet ofnonmagnetic material, coil springs, etc.

Moreover it is obvious that the above-illustrated different possiblevariations as to number, shape and arrangement of the mobile and fixedpoles and as to the type of lifter (electromagnet, electropermanent orpermanent magnet) can be freely combined thus leading to a great designflexibility with the capacity of adapting to multiple operatingrequirements.

1-6. (canceled)
 7. A magnetic lifter characterized in that it includesat least one dipolar mobile pole consisting of two ferromagnetic polepieces joined through an elastic connection and inserted between twofixed opposite poles so as to be able to slide within a housing formedbetween said two fixed opposite poles.
 8. A magnetic lifter according toclaim 1, wherein the elastic connection consists of an elastomer.
 9. Amagnetic lifter according to claim 2, wherein the elastic connection ismade of vulcanized rubber with a Shore hardness in the range from 50 to60.
 10. A magnetic lifter according to claim 1, characterized in that itincludes a plurality of independent dipolar mobile poles aligned andenclosed between only two fixed opposite poles.
 11. A magnetic lifteraccording to claim 4, wherein the elastic connection of the dipolarmobile poles consists of an elastomer.
 12. A magnetic lifter accordingto claim 5, wherein said elastic connection is made of vulcanized rubberwith a Shore hardness in the range from 50 to
 60. 13. A magnetic lifteraccording to claim 1, characterized in that it includes at least twodipolar mobile poles arranged one to the side of the other which share acentral two-faced fixed pole.
 14. A magnetic lifter according to claim7, wherein the elastic connection of the dipolar mobile poles consistsof an elastomer.
 15. A magnetic lifter according to claim 8, whereinsaid elastic connection is made of vulcanized rubber with a Shorehardness in the range from 50 to
 60. 16. A magnetic lifter according toclaim 1, characterized in that it includes at least one further fixedpole which operates in cooperation with one of the two fixed oppositepoles that act as sliding guide for one or more dipolar mobile poles.17. A magnetic lifter according to claim 10, wherein said fixed polewhich operates in cooperation with said further fixed pole has a greaterwidth than the other of the two fixed opposite poles that act as slidingguide.